Systems for monitoring pupil size and pupil responsiveness characteristics are well known in the art and are generally referred to as pupillometry systems or, simply, pupillometers. One early Pupillometer is described in U.S. Pat. No. 3,533,683, which issued to Stark et al. on Oct. 13, 1970 and is entitled “Dynamic Pupillometers Using Television Camera System” (incorporated herein by reference). The Stark et al. system employed a television camera system, a digital computer system, an infrared light source, and a visual light stimulator for determining the instantaneous size of a pupil as an eye (or neurologic pupillary control system) of a patient was exposed to various stimuli.
More advanced hand-held pupillometers are now commercially available and can be used in many applications including critical care, anesthesiology, research, and refractive surgery and opthalmology. One example is the PLR-100™ Pupillometer by Neuroptics®. The PLR-100™ pupillometer is a hand-held and cordless device which measures pupil size and dynamics. It can be used for either a static pupil measurement protocol (i.e., reporting pupil size measurements such as weighted average pupil size and standard deviation) as well as a dynamic pupil measurement protocol (i.e., reporting pupil light reflex measurements including: maximum pupil size before constriction, minimum pupil size after constriction; percent constriction, average constriction velocity, maximum constriction velocity, dilation velocity and time to reach 75% of the initial maximum pupil size after the constriction). The user can adjust the light stimulus intensity and duration. Numerical results are displayed on a color LCD numerically and graphically. Measurements may also be printed to a portable printer via infrared (wirelessly) transmission.
One area of pupillary clinical diagnosis and monitoring that has gained increased attention over the years is detecting and monitoring differences in size and asymmetry in pupillary response to stimulus between the left and right pupils. This condition where the sizes of the left and right pupils of an individual at rest are unequal is called anisocoria. A variety of potential causes for anisocoria exist, ranging from trivial or normal variation, to life threatening conditions, such as increased intracranial pressure (ICP) and brain swelling from a head injury, uncal herniation, lesions, and aneurismal compression. In general all those neurological conditions affecting the efferent pathway of the pupil system starting from the oculomotor nuclei in the midbrain up to the pupil sphincter muscle can be a cause of anisocoria.
Asymmetry in pupillary response is when the left and right pupils respond to a stimulus, such as a light stimulus, in different ways that go beyond the definition of anisocoria. For example, the pupil size between the left and right pupils at rest may be the same or very close in size, but the two pupils may react to a stimulus very differently, such as having different maximum pupil size before constriction, minimum pupil size after constriction, percent constriction, average constriction velocity, maximum constriction velocity, dilation velocity and time to reach 75% of the initial maximum pupil size after the constriction. Like anisocoria, asymmetry in pupillary response may also be indicative of an underlying medical condition.
Because anisocoria and asymmetry in pupillary response may be symptoms in some cases of very serious and immediately life threatening conditions, it is important for medical practitioners to have tools for easy, quick and convenient ways to accurately detect, measure, and view in real-time differences in pupillary size and pupillary reaction to stimulus between the right and left pupils. There are, unfortunately, very few such tools presently available. Thus, there is a need for high-tech instruments that can perform such functions. The methods, systems and devices of the present disclosure meet this and other such needs in the art.